Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Sunday, March 20, the first day of spring, at 7:00 AM. Today’s advisory is sponsored by Spark 1 and Beartooth Powder Guides. This advisory does not apply to operating ski areas.
Under clear skies westerly winds are light and temperatures dropped from a yesterday’s high near 40F to the upper 20s this morning (upper teens outside Cooke City). Today will be sunny and warm with mountain temperatures reaching the mid-40s. Winds will remain 10-15 mph out of the W-SW and clouds will roll in tonight, but no precipitation is expected. Today, the danger of getting a sunburn is rated CONSIDERABLE.
Wet Avalanche Danger
Today will be sunny, calm and unseasonably warm with mountain temperatures forecasted to reach well above freezing. Slopes that are fully exposed to sunshine will quickly become wet resulting in loose avalanches this afternoon. Roller balls and pinwheels of snow are a sign that the surface snow is getting wet and weak. All wet snow is weak snow. Throughout our advisory area the wet snow avalanche danger will be non-existent during the frozen hours of the morning, but trend to CONSIDERABLE on all slopes getting direct sun by early-afternoon.
Southern Madison Range Southern Gallatin Range
Lionhead area near West Yellowstone
In the southern mountains there are two weak layers buried in the snowpack. One is a faceted layer found 1-2 feet deep around an ice crust and the other is buried surface hoar, now under 2-4 feet of snow. These layers are unstable on some slopes as evidenced by the recent natural avalanche activity around Cooke City: an avalanche on Barronette Peak in YNP yesterday (photo); a large avalanche on Mt Fox, likely triggered by a cornice breaking on Friday; a few avalanches up Republic Creek on Wednesday (photo). Avalanches, reports of collapsing and cracking, plus Alex finding unstable surface hoar around Lionhead (video) are signs that some slopes are still dangerous. Today, the snowpack will be extra fickle because changes in the snowpack happen quickly when air temperatures are above freezing. I recommend staying off slopes that are wet, going elsewhere if you get collapsing or cracking, giving cornices a wide berth and digging for weak layers. For today, the dry snow avalanche danger is rated MODERATE on all slopes.
Bridger Range Northern Madison Range Northern Gallatin Range
The northern mountains have a stable snowpack and generally safe conditions. Many folks have been out in the backcountry and have found good skiing and riding on the 1-2 feet of powder that fell last week. On Friday, Eric toured around Mt Blackmore and found the new snow was bonded well to the old surface. In his video he explains that the main avalanche problem will be wet slides, which will spike today. Alex toured up Hyalite yesterday an echoed Eric’s concern: the powder is fresh ammunition for wet slides, but otherwise stable. For today the dry snow avalanche danger is rated LOW on all slopes.
I will issue the next advisory tomorrow morning by 7:30 a.m. If you have any snowpack or avalanche observations to share, drop us a line at mtavalanche@gmail.com or leave a message at 587-6984.